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package java.lang.management;

import javax.management.openmbean.CompositeData;
import java.util.concurrent.locks.*;
import sun.management.LockInfoCompositeData;

/**
 * Information about a <em>lock</em>.  A lock can be a built-in object monitor,
 * an <em>ownable synchronizer</em>, or the {@link Condition Condition}
 * object associated with synchronizers.
 * <p>
 * <a name="OwnableSynchronizer">An ownable synchronizer</a> is
 * a synchronizer that may be exclusively owned by a thread and uses
 * {@link AbstractOwnableSynchronizer AbstractOwnableSynchronizer}
 * (or its subclass) to implement its synchronization property.
 * {@link ReentrantLock ReentrantLock} and
 * {@link ReentrantReadWriteLock ReentrantReadWriteLock} are
 * two examples of ownable synchronizers provided by the platform.
 *
 * <h3><a name="MappedType">MXBean Mapping</a></h3>
 * <tt>LockInfo</tt> is mapped to a {@link CompositeData CompositeData}
 * as specified in the {@link #from from} method.
 *
 * @author Mandy Chung
 * @see java.util.concurrent.locks.AbstractOwnableSynchronizer
 * @see java.util.concurrent.locks.Condition
 * @since 1.6
 */

public class LockInfo {

  private String className;
  private int identityHashCode;

  /**
   * Constructs a <tt>LockInfo</tt> object.
   *
   * @param className the fully qualified name of the class of the lock object.
   * @param identityHashCode the {@link System#identityHashCode identity hash code} of the lock
   * object.
   */
  public LockInfo(String className, int identityHashCode) {
    if (className == null) {
      throw new NullPointerException("Parameter className cannot be null");
    }
    this.className = className;
    this.identityHashCode = identityHashCode;
  }

  /**
   * package-private constructors
   */
  LockInfo(Object lock) {
    this.className = lock.getClass().getName();
    this.identityHashCode = System.identityHashCode(lock);
  }

  /**
   * Returns the fully qualified name of the class of the lock object.
   *
   * @return the fully qualified name of the class of the lock object.
   */
  public String getClassName() {
    return className;
  }

  /**
   * Returns the identity hash code of the lock object
   * returned from the {@link System#identityHashCode} method.
   *
   * @return the identity hash code of the lock object.
   */
  public int getIdentityHashCode() {
    return identityHashCode;
  }

  /**
   * Returns a {@code LockInfo} object represented by the
   * given {@code CompositeData}.
   * The given {@code CompositeData} must contain the following attributes:
   * <blockquote>
   * <table border summary="The attributes and the types the given CompositeData contains">
   * <tr>
   * <th align=left>Attribute Name</th>
   * <th align=left>Type</th>
   * </tr>
   * <tr>
   * <td>className</td>
   * <td><tt>java.lang.String</tt></td>
   * </tr>
   * <tr>
   * <td>identityHashCode</td>
   * <td><tt>java.lang.Integer</tt></td>
   * </tr>
   * </table>
   * </blockquote>
   *
   * @param cd {@code CompositeData} representing a {@code LockInfo}
   * @return a {@code LockInfo} object represented by {@code cd} if {@code cd} is not {@code null};
   * {@code null} otherwise.
   * @throws IllegalArgumentException if {@code cd} does not represent a {@code LockInfo} with the
   * attributes described above.
   * @since 1.8
   */
  public static LockInfo from(CompositeData cd) {
    if (cd == null) {
      return null;
    }

    if (cd instanceof LockInfoCompositeData) {
      return ((LockInfoCompositeData) cd).getLockInfo();
    } else {
      return LockInfoCompositeData.toLockInfo(cd);
    }
  }

  /**
   * Returns a string representation of a lock.  The returned
   * string representation consists of the name of the class of the
   * lock object, the at-sign character `@', and the unsigned
   * hexadecimal representation of the <em>identity</em> hash code
   * of the object.  This method returns a string equals to the value of:
   * <blockquote>
   * <pre>
   * lock.getClass().getName() + '@' + Integer.toHexString(System.identityHashCode(lock))
   * </pre></blockquote>
   * where <tt>lock</tt> is the lock object.
   *
   * @return the string representation of a lock.
   */
  public String toString() {
    return className + '@' + Integer.toHexString(identityHashCode);
  }
}
